Nickel base superalloys are widely used in gas turbine engines and have evolved greatly over the last 50 years. As used herein the term superalloy will mean a nickel base superalloy containing a substantial amount of the gamma prime (Ni.sub.3 Al) strengthening phase, preferably from about 30 to about 50 volume percent of the gamma prime phase.
Processing techniques for superalloys have also evolved and many of the newer processes are quite costly.
U.S. Pat. No. 3,519,503 describes an isothermal forging process for producing complex superalloy shapes. This process is currently widely used, and as currently practiced requires that the starting material be produced by powder metallurgy techniques. The reliance on powder metallurgy techniques makes this process expensive.
U.S. Pat. No. 4,574,015 deals with a method for improving the forgeability of superalloys by producing overaged microstructures in such alloys. The gamma prime phase particle size is greatly increased over that which would normally be observed.
U.S. Pat. No. 4,579,602 deals with a superalloy forging sequence which involves an overage heat treatment.
U.S Pat. No. 4,769,087 describes another forging sequence for superalloys which includes an overage step.
U.S. Pat. No. 4,612,062 describes a forging sequence for producing a fine grained article from a nickel base superalloy. The process includes a first deformation step at a temperature above the gamma prime solvus and a second deformation step at a temperature below the gamma prime solvus with specified strain rates and deformation amounts.
U.S. Pat. No. 4,453,985 describes an isothermal forging process which produces a fine grain product.
U.S. Pat. No. 2,977,222 describes a class of superalloys which are similar to those to which the invention process has particular applicability.